A Syrian monitoring group has said at least 32 Syrian rebel fighters were killed when a suicide bomber attacked their bus near the border with Turkey on August 14.

The Syrian Observatory for Human Rights said on August 15 that the attacker detonated an explosive on the bus as it was carrying rebel fighters into Syria via the Atmeh border crossing, about 40 kilometers from the embattled city of Aleppo.

At least two Turkish border guards were also reportedly killed in the blast. There were no reports on the number of injured.

Also on August 15, a social-media channel associated with the Islamic State (IS) extremist group claimed responsibility for the attack and said more than 50 people had been killed.

The statement charged that the rebel fighters were on their way to Syria to fight against IS in northern Aleppo province.

Syria's Idlib Province, where Atmeh is located, is a major bastion of the Turkey-backed opposition to President Bashar al-Assad's rule.